Anisotropy, disorder, and superconductivity in CeCu<sub>2</sub>Si<sub>2</sub>under high pressure

Holmes, A. T.; Jaccard, D.; Jeevan, H. S.; Geibel, C.; Ishikawa, Masayasu

doi:10.1088/0953-8984/17/35/009

Cited by 9 publications

(8 citation statements)

References 26 publications

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“…Moreover, at this V magnetic order is still present in CeAu 2 Si 2 but is absent in CeCu 2 Si 2 , which supports the idea that magnetic order and SC are not directly related [6]. For ρ 0 > 50 µΩcm, the depression of T bulk c of CeCu 2 Si 2 with increasing ρ 0 becomes much weaker, and SC survives even when ρ 0 is of the order of the Ioffe-Regel limit [34]. However, the large ρ 0 could be due to the effect of Kondo holes [35,36], and thus is no longer a good indication of the level of disorder.…”

Section: Comparison With the Results Of Ceau2si2(sn)supporting

confidence: 70%

Effect of disorder on the pressure-induced superconducting state ofCeAu2Si2

et al. 2015

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CeAu2Si2 is a newly discovered pressure-induced heavy fermion superconductor which shows very unusual interplay between superconductivity and magnetism under pressure. Here we compare the results of high-pressure measurements on single crystalline CeAu2Si2 samples with different levels of disorder. It is found that while the magnetic properties are essentially sample independent, superconductivity is rapidly suppressed when the residual resistivity of the sample increases. We show that the depression of bulk Tc can be well understood in terms of pair breaking by nonmagnetic disorder, which strongly suggests an unconventional pairing state in pressurized CeAu2Si2. Furthermore, increasing the level of disorder leads to the emergence of another phase transition at T * within the magnetic phase, which might be in competition with superconductivity.

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Section: Comparison With the Results Of Ceau2si2(sn)supporting

confidence: 70%

Effect of disorder on the pressure-induced superconducting state ofCeAu2Si2

et al. 2015

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“…42 Around p V , the maximum T onset c and T ρ=0 c coincide. Above p V , in several samples 3,41,43 the superconducting region extends to high p; that is, the decrease of T onset c (p > p V ) is less steep than shown in Fig. 1, but may exhibit a jump close to 8 GPa.…”

Section: General Relevancy Of ρ( P) Analysismentioning

confidence: 82%

Heavy fermion superconductor CeCu2Si2under high pressure: Multiprobing the valence crossover

Seyfarth

Rüetschi²,

Sengupta³

et al. 2012

Phys. Rev. B

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The first heavy fermion superconductor CeCu 2 Si 2 has not revealed all its striking mysteries yet. At high pressures, superconductivity is supposed to be mediated by valence fluctuations, in contrast to ambient pressure, where spin fluctuations most likely act as pairing glue. We have carried out a multiprobe (electric transport, thermopower, ac specific heat, Hall and Nernst effects) experiment up to 7 GPa on a high-quality CeCu 2 Si 2 single crystal. For the first time, the resistivity data make it possible quantitatively to draw the valence crossover line within the p-T plane and to locate the critical end point at 4.5 ± 0.2 GPa and a slightly negative temperature. In the same pressure region, remarkable features have also been detected in the other physical properties, presumably acting as further signatures of the Ce valence crossover and the associated critical fluctuations: We observe maxima in the Hall and Nernst effects and a sign change and a strong sensitivity on magnetic field in the thermopower signal.

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“…36) CeCu 2 Si 2 has been the subject of intensive study by the authors, in which we showed that the enhancement of T c under pressure was linked to a sharp Ce valence transition. 8,[37][38][39][40][41][42] The link between superconductivity and valence change had been noted by Jaccard and coworkers since the first measurements of CeCu 2 Si 2 under high pressure in 1984. 43) The isostructural sister compound CeCu 2 Ge 2 was shown to behave in a very similar way, with a shift of around 10 GPa corresponding to the larger atomic size of Ge.…”

Section: Cecu 2 Simentioning

confidence: 99%

Valence Instability and Superconductivity in Heavy Fermion Systems

2007

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Many cerium-based heavy fermion (HF) compounds have pressure–temperature phase diagrams in which a superconducting region extends far from a magnetic quantum critical point. In at least two compounds, CeCu 2 Si 2 and CeCu 2 Ge 2 , an enhancement of the superconducting transition temperature was found to coincide with an abrupt valence change, with strong circumstantial evidence for pairing mediated by critical valence, or charge transfer, fluctuations. This pairing mechanism, and the valence instability, is a consequence of a f – c Coulomb repulsion term U fc in the Hamiltonian. While some non-superconducting Ce compounds show a clear first order valence instability, analogous to the Ce α–γ transition, we argue that a weakly first order valence transition may be a general feature of Ce-based HF systems, and both magnetic and critical valence fluctuations may be responsible for the superconductivity in these system

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Anisotropy, disorder, and superconductivity in CeCu₂Si₂under high pressure

Cited by 9 publications

References 26 publications

Effect of disorder on the pressure-induced superconducting state ofCeAu2Si2

Effect of disorder on the pressure-induced superconducting state ofCeAu2Si2

Heavy fermion superconductor CeCu2Si2under high pressure: Multiprobing the valence crossover

Valence Instability and Superconductivity in Heavy Fermion Systems

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Anisotropy, disorder, and superconductivity in CeCu2Si2under high pressure

Cited by 9 publications

References 26 publications

Effect of disorder on the pressure-induced superconducting state ofCeAu2Si2

Effect of disorder on the pressure-induced superconducting state ofCeAu2Si2

Heavy fermion superconductor CeCu2Si2under high pressure: Multiprobing the valence crossover

Valence Instability and Superconductivity in Heavy Fermion Systems

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Anisotropy, disorder, and superconductivity in CeCu₂Si₂under high pressure